| Most of the existing methods for calculating dc ionized fields of monopolar and bipolar corona have ignored the ionization regions and excluded the transient phenomena of corona discharges. In this dissertation, the high voltage dc (HVdc) bipolar corona problem was studied with a two-dimensional particle-in-cell simulation, which allowed us to model the time dependent nonlinear behavior and microscopic phenomena involved in the corona discharge (impact ionization, attachment, mobility, conduction current, displacement current, etc.). The technique follows simulation particles that represent electrons, positive ions, and negative ions, and self-consistently calculates the associated electric field that determines the particle motion. Finite element and charge simulation methods were used to solve Poisson's equation while a finite difference scheme was applied to move simulation particles. Multi-scale techniques (nonuniform triangle mesh and variable time step) were employed to reduce numerical noise and increase simulation efficiency.; The particle-in-cell simulation was successfully applied to a cylindrical bipolar corona cage problem. Simulation results included one primitive streamer, multi-electrode induced currents, conductor temperature effects, memory effects, approach to a stationary state, corona saturation on a transient basis, and electric parameters that characterize the dc corona environment (electric field intensity, ion current density, space charge density).; Characteristics of the corona current were also obtained through measurements in the laboratory corona cage. Digitizing oscilloscopes have been used to view the anode and cathode corona current at {dollar}pm 60kV{dollar} and {dollar}pm 64kV.{dollar} Cathode current appeared as a nearly quiescent dc current with electron current pulses located at time intervals on the order of 15{dollar}mu s.{dollar} Anode current also appeared as a nearly quiescent dc current with electron current pulses located at time intervals on the order of 800{dollar}mu s.{dollar} Anode pulses were observed to be about 30 times larger than cathode pulses. Both the laboratory experiment and the particle-in-cell simulation were used to study the influence of load current on corona. |
